Vue 3 Event Bus with Composition API

Question

I have setup mitt and trying to dispatch event to another component but I am having hard time because in the setup() method it doesn't have this for accessing app instance.

Here is what I tried:

import App from './App.vue'
const el = document.getElementById('app')

import mitt from 'mitt';
const emitter = mitt();

const app = createApp(App)
app.config.globalProperties.emitter = emitter;
app.mount(el);

And in the component, I want to dispatch an event

export default {
   setup() {
      function toggleSidebar() {
          this.emitter.emit('toggle-sidebar');

          console.log(this); // binds to setup(), not the vue instance.
      }
   }
}

As this doesn't exist, I can't access the .emitter. What am I missing? How to use officially suggested mitt in Vue 3 composition api?

---

By the way if I use the v2 syntax, I can access this.emitter. But I am curious about Composition API way

export default {
  mounted() {
    console.log(this.emitter); // works
  }
} 

Answer 1

You may be able to use getCurrentInstance to get the global property

component:

import { getCurrentInstance } from 'vue';
export default {
  setup() {
    // get current instance
    const internalInstance = getCurrentInstance(); 
    // get the emitter from the instance
    const emitter = internalInstance.appContext.config.globalProperties.emitter;
  }
} 

Answer 2

So far I have used this code to make the "emitter" available.

//main.ts
import mitt from 'mitt'
const emitter = mitt()
export default emitter

And then inside the components I use

import emitter from '@/main';

This worked so far in Vue2 and Vue3 - at least with the options API.

I have to admit though that I currently run into some trouble with the new vite server and the hot module reload (hmr). Is this style suboptimal in any way?